Cavity type magnetrons



May 8, 1956 R. DUNSMUIR CAVITY TYPE MAGNETRONS Filed 001;. 1-1, 1954Fig.2

lNVE/V TOR ROBERT DU/V6MU/R United States Patent CAVITY TYPE MAGNETRONSRobert Dunsmuir, Rugby, England, assignor to The British Thomson-HoustonCompany Limited, a British company Application October 11, 1954, SerialNo. 461,572

4 Claims. (Cl. PAS-39.69)

This invention relates to multi-cavity magnetrons of the type having ananode comprising a series of cavity resonators. More particularly, theinvention relates to such magnetrons in which the anode cavityresonators are formed by a series of circumferentially spaced vanes.

In such cavity type magnetrons there is a tendency to resonate inseveral modes having slightly different wavelengths.

In many cases the frequency discriminating properties of the magnetronmay be insufiicient to suppress the unwanted modes with the result thatunwanted frequencies may occur in the output.

In order to eliminate such unwanted frequencies, strapping has beenemployed, although other physical solutions of this problem have beenemployed in the art. The system of strapping generally used providescircumferentially extending ring straps, generally of toroidal shape. Aplurality of such straps is positioned axially along the length of theanode, the planes in which such straps lie being substantially parallel.Each strap is normally connected to each alternate vane or segment andadjacent straps are normally connected to the opposite sets of vanes orsegments.

Each ring passes through all the vanes but only makes contact withalternate vanes and passes through apertures in the intervening vaneswithout making contact. Such intervening vanes are connected by theadjacent straps.

The main object of the invention is to provide an improved arrangementfor eliminating modes other than the 1r mode in magnetron oscillators ofthe type under consideration. More particularly, it is an object of thepresent invention to provide an improved end strap or ring constructionto improve the elimination of such other modes.

The present invention provides a multi-cavity type magnetron of the kindhaving an anode of cylindrical form and comprising a series ofcircumferentially displaced segments or vanes and a series of axiallydisplaced ring straps whereof each strap contacts only alternatesegments or vanes, and in which the end strap has provided meansdefining a break or gap between a pair of segments and is electricallyconnected to the adjacent segment on each side of the break or gaps.

Preferably the break extends substantially from one of the segments to apoint midway between the pair of segments, i. e., from one of thesegments to the center of the cavity resonator formed by this segmentand an adjacent segment or vane.

The break is preferably in the cavity resonator opposite the outputcavity resonator.

It will be appreciated that in the case of a vane type anode in whichthe ring passes through a clearance hole in alternate vanes there willbe such a clearance hole on one side of each cavity resonator and inapplying the invention it will be necessary to conductively seal theclearance hole in the side of the break in order that the end strap maybe electrically connected to each of the adjacent segments or vanes.

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In order that the invention may be more fully understood, reference willnow be made to the accompanying drawings, in which:

Fig. 1 shows a diagram in plan of the end strap of a multi-cavitymagnetron and its connections to the anode structure according to theinvention.

Fig. 2 is a part section on the line 22 of Fig. 1 of a segment or vaneof the magnetron.

In the drawings a multi-cavity type magnetron has an anode 1 containingsegments or vanes 2 enclosing cavities or cavity resonators 3. Ringstraps 4 pass through the vanes, making electrically conductiveconnections 5 with alternate vanes and passing through apertures 6 inthe intervening vanes without connection, these apertures 6 beingradially enlarged relative to the apertures 16 in the vanes in whichconnections 5 are made. Adjacent straps are connected to alternate vanesas shown.

At least one of the upper or lower ends of the axially extending anodeis provided with an end strap 7 having ends 8 and 9 defining a break orgap 10 which is made in cavity resonator 11 opposite to the outputcavity resonator 12. The break 10 extends from one segment half-wayacross cavity resonator 11. The end strap 7 is electrically connected toboth of the adjacent segments 13 and 14. The connection to 13 is normaland an additional connection 15 is made to segment 14 by sealing theaperture with electrically conductive material.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

l. A multi-cavity-type magnetron having an anode of cylindrical form,said anode comprising a series of circumferentially displaced segmentsdefining a series of cavity resonators, a first ring strap concentricwith said anode, said strap passing through said segments, connectionsbetween said strap and alternate segments, a second ring strap parallelto said first ring strap, connections between said second ring strap andintervening segments, an end strap, means defining a gap in the said endstrap in a particular cavity resonator, and connections from said endstrap on opposite sides of said gap to respective segments defining saidcavity resonator.

2. A cavity-type magnetron having an anode of cylindrical form, saidanode comprising a series of circumferentially displaced segmentsdefining a series of cavity resonators, a plurality of ring strapsconcentric with said anode, said straps passing through said segments,connections between alternate straps and alternate segments, andconnections between the intervening straps and intervening segments, anend strap, means defining a gap in said end strap in a particular cavityresonator, and connections from said end strap on opposite sides of saidgap to respective segments defining said cavity resonator.

3. A cavity-type magnetron having an anode of cylindrical form, saidanode comprising a series of circumferentially displaced segmentsdefining a series of cavity resonators, a plurality of ring strapsconcentric with said anode, said straps passing through said segments,connections between alternate straps and alternate segments andconnections between the intervening straps and intervening segments, anend strap, said end strap having ends in a cavity resonator defining abreak in said end strap, one end being adjacent a segment and the otherend being substantially midway between the segments defining said cavityresonator, and connections from said strap ends to each of saidsegments. I

4. A cavity-type magnetron having an anode of cylindrical form, saidanode comprising a series of circumferentially displaced segmentsdefining a series of cavity resonators, output means, said output meansbeing situated in an output cavity resonator, a plurality of ring strapsconcentric with said anode, said straps passing through said segments,connections between alternate straps and alternate segments andconnections between the intervening straps and intervening segments, anend strap, said end strap having ends in a second cavity resonatordefining a break in said end strap, said cavity resonator being oppositethe said output cavity, one end being adjacent a segment and the otherend being substantially midway between the segments defining said secondcavity resonator, and connections from said strap ends to each of saidsegments.

References Cited in the file of this patent UNITED STATES PATENTS

